GEOG 595 rayshader Examples by Jasper Zhou

Import the required libraries.

library(rayshader)

Warning: package ‘rayshader’ was built under R version 4.4.3Registered S3 methods overwritten by 'htmltools':
  method               from         
  print.html           tools:rstudio
  print.shiny.tag      tools:rstudio
  print.shiny.tag.list tools:rstudio
Registered S3 method overwritten by 'htmlwidgets':
  method           from         
  print.htmlwidget tools:rstudio

library(terra)

terra 1.8.15

library(rgl)

Warning: package ‘rgl’ was built under R version 4.4.3

Loading DEM

# Download & Load the DEM from GitHub
dem_url <- "https://github.com/Fangsheng-Zhou/rayshader_exploration/raw/refs/heads/main/Example_DEM_Data/USGS_13_n49w122_20230307_mtbaker.tif"
dest_file <- "Data/mtbaker_dem.tif"

# Download and save DEM
download.file(dem_url, destfile = dest_file, mode = "wb")

trying URL 'https://github.com/Fangsheng-Zhou/rayshader_exploration/raw/refs/heads/main/Example_DEM_Data/USGS_13_n49w122_20230307_mtbaker.tif'
Content type 'application/octet-stream' length 20654132 bytes (19.7 MB)
downloaded 19.7 MB

# Read the DEM as a raster
mtbaker_dem <- rast(dest_file)

# Plot the DEM as a grayscale image to verify
plot(mtbaker_dem, main = "Mt Baker DEM")

Downsize DEM for faster rendering

# Downsample DEM by a factor of 3 
mtbaker_dem_downsampled <- aggregate(mtbaker_dem, fact = 3, fun = mean) 

plot(mtbaker_dem_downsampled, main = "Mt Baker Downsampled DEM")

Note: you can compare the before and after DEM using res() or ncell().

Create a 2D plot of the DEM using rayshader.

# Convert to rayshader-compatible matrix
elmat <- raster_to_matrix(mtbaker_dem_downsampled)

[1] "Dimensions of matrix are: 603x863"

# Apply shading and plot the 2D rayshader map
elmat %>%
  sphere_shade(texture = "desert") %>%
  plot_map()

How about adding some shadow?

# Apply texture and simple ray-traced shadows
elmat %>%
  sphere_shade(texture = "desert") %>%
  add_shadow(ray_shade(elmat), 0.5) %>% # Adds realistic lighting effects
  plot_map()

How about plot it in 3D?

# Render in 3D 
elmat %>%
  sphere_shade(texture = "desert") %>%
  add_shadow(ray_shade(elmat), 0.5) %>% # Adds realistic lighting effects
  plot_3d(elmat, zscale = 10, fov = 0, theta = 135, zoom = 0.75, phi = 45, windowsize = c(1000, 800))

# Pause briefly before taking a snapshot
Sys.sleep(3)

# Save a high-quality snapshot
render_snapshot("Data/mtbaker_3D.png")

Add water

elmat %>%
  sphere_shade(texture = "desert") %>%
  add_water(detect_water(elmat, cutoff = 0.3), color = "blue") %>%  # Adjust cutoff
  add_shadow(ray_shade(elmat), 0.5) %>% 
  plot_3d(elmat, zscale = 10, fov = 0, theta = 135, zoom = 0.75, phi = 45, windowsize = c(1000, 800))

2D vs. 3D plots, side by side comparison

library(ggplot2)
library(rayshader)

mtplot = ggplot(mtcars) + 
  geom_point(aes(x = mpg, y = hp, color = cyl)) + 
  scale_color_continuous(limits = c(0, 8))

par(mfrow = c(1, 2))
plot_gg(mtplot, width = 3.5, raytrace = FALSE, preview = TRUE)

plot_gg(mtplot, width = 3.5, multicore = TRUE, windowsize = c(800, 800), 
        zoom = 0.85, phi = 35, theta = 30, sunangle = 225, soliddepth = 0.5)

That’s all for the quick examples!